Light absorbent agent polymer useful for organic anti-reflective coating, its preparation method and organic anti-reflective coating composition comprising the same

ABSTRACT

Disclosed are a light absorbent agent polymer for organic anti-reflective coating which can prevent diffused light reflection of bottom film layer or substrate and reduce standing waves caused by variation of thickness of the photoresist itself, thereby, increasing uniformity of the photoresist pattern, in a process for forming ultra-fine patterns of photoresist for photolithography by using 193 nm ArF among processes for manufacturing semiconductor device, and its preparation method. Also, the present invention discloses an organic anti-reflective coating composition comprising the light absorbent agent polymer for the organic anti-reflective coating and a pattern formation process using the coating composition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light absorbent agent polymer usefulfor an organic anti-reflective coating which can prevent diffused lightreflection of the bottom film layer or substrate and reduce standingwaves caused by a variation of thickness of the photoresist itself,thereby, increasing uniformity of the photoresist pattern, in a processfor forming ultra-fine patterns of photoresist for photolithography byusing 193 nm ArF among processes for manufacturing semiconductor device,and its preparation method.

Also, the present invention provides an organic anti-reflective coatingcomposition (hereinafter abbreviated as “the coating composition”)comprising the light absorbent agent polymer for the organicanti-reflective coating (hereinafter abbreviated as “the coatingpolymer”) and a pattern formation process using the coating composition.

2. Description of the Related Art

In a fabrication process of ultrafine patterns for preparingsemiconductor devices, standing waves and reflective notching inevitablyoccur due to the optical properties of the lower film layer on thephotoresist film and due to the thickness changes in the photosensitivefilm. In addition, there is another problem in that a CD (criticaldimension) alteration is caused by diffracted and reflected light fromthe lower film layers. Thus, it has been suggested to introduce ananti-reflective coating that prevents back reflection at a lower filmlayer between a lower film and a photoresist by introducing organicmaterial with high absorbance at a wavelength range of the lightemployed as a light source.

Especially, when exposed to UV light from the light source, a thinphotoresist film is transmitted by the UV light, thus allowing lightabsorbed in the bottom portion of the thin film to be scattered and/orreflected. Such an anti-reflective coating can absorb the scatteredand/or reflected light and, thereby, directly affecting the fineprocessing of the photoresist.

Anti-reflective coatings are classified into inorganic and organicanti-reflective coatings depending on the material used, or intoabsorptive and interfering anti-reflective coatings based on theoperation mechanism. For a fine pattern forming process using I-line(365 nm wavelength) radiation, inorganic anti-reflective coating arepredominantly used, while TiN and amorphous carbon (a-C) are employed asan absorptive system anti-reflective coating and SiON are employed as aninterfering system anti-reflective coating. In a fabrication process ofultrafine patterns using KrF light (248 nm), an inorganicanti-reflective coating has been mainly used and an organicanti-reflective coating has been used occasionally along with theinorganic anti-reflective coating.

However, in an ultra-fine pattern forming process using ArF light (193nm), no proper anti-reflective coating has been developed yet.Especially, in the case of an inorganic anti-reflective coating, nomaterial is known which enables the control of the interference at 193nm, the wavelength of the light source. Thus, there has been great dealof effort to employ an organic compound as an anti-reflective coating.

To be a good organic anti-reflective coating, the following conditionsmust be satisfied.

First, an anti-reflective coating must not be dissolved by the solventof the photoresist in the process of laminating an anti-reflectivecoating and then coating the photoresist on the top portion thereof. Inorder to achieve this goal, such an anti-reflective coating must bedesigned to form a cross-linked structure without producing any chemicalby-product, in a process of lamination an anti-reflective coating bycoating an anti-reflective coating composition and then performing abaking process.

Second, in order to prevent diffused light reflection from the bottomfilm layer, the coating must contain certain materials to absorb lightat the wavelength range of the exposure light source.

Third, no flowing in or out of chemicals such as acid or amine must notcome-in or go-out from the anti-reflective coating. This is because whenacid migrates from the anti-reflective coating to a photoresist film ofan unexposed part, undercutting occurs at a lower part of the patternwhile footing may occur when a base such as amine migrates to thephotoresist film. Such a phenomenon can be stopped by preventing suchchemicals from coming into or going out of the anti-reflective coating.

Fourth, the etching speed of the anti-reflective coating should befaster than the etching speed of the upper photosensitive film so as tofacilitate the etching process by using the photosensitive film as amask.

Finally, the anti-reflective coating must be as thin as possible to theextent as to sufficiently play a role as an anti-reflective coating.

In order to satisfy the above requirements, conventional organicanti-reflective coating compositions generally comprise a cross-linkingagent to allow the anti-reflective coating to have a cross-linkedstructure, a light-absorbing agent to absorb the light at the wavelengthrange of exposure light source, a thermal acid generator as a catalystfor activating the cross-linking reaction, and an organic solvent.

As mentioned above, it requires a novel organic anti-reflective coatingpreferably useable as the anti-reflective coating for the ArF lightsource at 193 nm, which can control the interference phenomenon on theArF light source. Therefore, the present inventors develop ananti-reflective coating polymer capable of controlling the interferencephenomenon to the ArF light source, as well as to satisfy all of therequirements mentioned above, and a composition comprising the coatingpolymer, thereby accomplishing the present invention.

SUMMARY OF THE INVENTION

The present invention is designed in consideration of the problems ofprior art mentioned above, and therefore it is an object of the presentinvention to provide a novel polymer useable as a light absorbent agentfor an organic anti-reflective coating in an ultrafine pattern formingprocess by using a ArF light source with 193 nm wavelength in asemiconductor device production process, and its preparation method.

In another aspect, it is another object of the present invention toprovide an organic anti-reflective coating composition comprising theorganic anti-reflective coating polymer, a pattern forming method usingthe same and a semiconductor device produced by the pattern formingmethod.

To achieve the above objects, the present invention provides a lightabsorbent agent polymer for an organic anti-reflective coatingrepresented by the following general formula I and having a weightaverage molecular weight in the range of 5,000 to 15,000.

-   -   wherein a and b represent the mole percentage of respective        monomers and a:b=5 to 95:5 to 95.

The polymer of formula I contains chromophore having a high absorbanceat the wavelength of 193 nm, and comprises maleic anhydride as a monomerstatus to sufficiently form a cross-linkage bond with a cross-linkingpolymer having an acetal functional group. Because of suchcharacteristics, the polymer of formula I can be preferably used as thelight absorbent agent in the organic anti-reflective coating compositionwith respect to the light source having a 193 nm wavelength. That is,since the polymer of formula I is included in the coating compositionfor serving as the light absorbing agent, it can control the lightinterference phenomenon during the ultra-fine pattern formation processusing the 193 nm light source. In addition, the polymer can easily formthe cross-linkage bond with the cross-linking polymer to givesolvent-resistant ability to the anti-reflective coating, therebyensuring improved photoresist patterns by employing the coatingcomposition containing such a light absorbent agent to form theanti-reflective coating.

As mentioned above, the polymer of formula I has a molecular weightranging from 5,000 to 15,000. If such a molecular weight is less than5,000, no sufficient cross-linkage bond will be generated at the formedanti-reflective coating will decrease the solvent-resistance of theanti-reflective coating. If the molecular weight is higher than 15,000,the viscosity of the polymer becomes higher, thereby causing difficultyin producing the anti-reflective coating composition resulting introuble with respect to application of the anti-reflective coatingcomposition.

The polymer of the formula I may be prepared by dissolving a maleicanhydride and 5,8-dihydroxy-1,4-naphthoquinone in an organic solvent,adding a polymerization initiator to the dissolved material, then,conducting free-radical polymerization under vacuum conditions, at 60 to70° C. for 6 to 12 hours.

The organic solvent for polymerization used in such a preparation methodpreferably includes at least one selected from a group consisting oftetrahydrofuran, cyclohexanone, dimethyl formamide, dimethyl sulfoxide,dioxane, methylethylketone, PGMEA, ethylacetate, benzene, toluene andxylene. The polymerization initiator used in the above method includesall of conventional radical initiators for the free-radicalpolymerization and, preferably, at least one selected from a groupconsisting of 2,2′-azobisisobutyronitrile (AIBN), benzoyl peroxide,acetyl peroxide, lauryl peroxide, t-butyl peracetate, t-butylhydroperoxide and di-t-butyl peroxide.

In another aspect of the present invention, there is provided an organicanti-reflective coating composition comprising: a light absorbent agentpolymer represented by the following formula I and having a weightaverage molecular weight in the range of 5,000 to 15,000; across-linking polymer represented by the following formula II and havingan average molecular weight in the range of 2,000 to 70,000; a thermalacid generator; and an organic solvent.

-   -   a and b represent the mole percent of respective monomers and        a:b=5 to 95:5 to 95.    -   wherein R₄ and R₅ represent independently alkyl groups having 1        to 10 carbon atoms substituted by branched chain or main chain;        R₃ is hydrogen or methyl group; and c:d=5 to 90 by mole: 10 to        95% by mole.

Briefly, the above coating composition of the present inventioncomprises the polymer represented by the formula I as the lightabsorbent agent, in which the maleic anhydride group contained in thepolymer of formula I can generate the cross-linkage bond with the acetalfunctional group contained in the cross-linking polymer of formula II,whereby the formed anti-reflective coating has the solvent-resistance.Also, by such a cross-linkage bond, it is possible to protect chemicalmaterials such as acid or amine from being transferred out of theanti-reflective coating, in turn, to minimize under-cutting and/orputting phenomenon to result in formation of an improved photoresistpattern. Furthermore, both of the polymers represented by formulas I andII comprise a chromophore having a remarkably high absorbance to absorblight reflected or diffused at bottom portion of the photoresist filmand to remarkably reduce standing wave effect caused by such reflectedand/or diffused light.

Such polymer of the formula II has been disclosed in Korean PatentApplication No. 2002-73648 filed by the applicant of the presentinvention, which is enclosed herewith in reference to a practicalprocedure for producing the same and characteristics thereof.

In the organic anti-reflective coating composition according to thepresent invention, such cross-linking polymer of the formula IIpreferably comprises at least one selected from a group consisting ofpolymers having the structures of formulae III to VI.

-   -   wherein a:b=5 to 90% by mole: 10 to 95% by mole.

In particular, since the polymers of formulae III to VI can activelygenerate the cross-linkage bonds with the light absorbent agent polymerhaving a maleic anhydride group in the presence of acid, it can be morepreferably employed as a cross-linking agent in the organicanti-reflective coating composition according to the present invention.

With respect to the organic anti-reflective coating composition of thepresent invention, such thermal acid generator may be one generally usedin conventional organic anti-reflective coating compositions and,preferably comprises a compound having a structure represented by thefollowing formula VII.

The thermal acid generator serves as a catalyst for activating suchcross-linking reactions between the above cross-linking agent and thelight absorbent agent. When a thermal process such as a baking processis carried out after applying such a thermal acid generator on a wafer,acid is generated from the thermal acid generator and, in the presenceof acid generated by the above process, the cross-linking reactionoccurs bringing about to form the organic anti-reflective coatinginsoluble in the solvent for the photoresist. In other words, it ispossible to accelerate the cross-linking reaction between the lightabsorbent agent and the cross-linking agent by employing the compound offormula VII as the thermal acid generator.

The organic solvent used in the organic anti-reflective coatingcomposition of the present invention preferably includes at least oneselected from a group consisting of methyl 3-methoxy propionate (MMP),ethyl 3-ethoxy propionate (EEP), propyleneglycol methylether acetate(PGMEA) and cyclohexanone.

In the organic anti-reflective coating composition of the presentinvention, the amount of the polymer represented by the formula I as thelight absorbent agent is preferably in the range of 0.3 to 70% by weightwith respect to the organic solvent contained in the anti-reflectivecoating composition and the amount of the polymer of formula II as thecross-linking agent is preferably in the range of 0.3 to 50% by weightwith respect to the organic solvent contained in the anti-reflectivecoating composition. Likewise, the amount of the thermal acid generatoris 0.5 to 40% by weight with respect to the total amount of the lightabsorbent agent and the cross-linking agent.

Therefore, when a baking process is carried out after applying theorganic anti-reflective coating composition comprising such componentsmentioned above with the composition rates on the wafer, acid from thethermal acid generator is generated and, the cross-linking reactionbrings out between the light absorbent agent polymer of formula I andthe cross-linking agent polymer of formula II by the acid generated fromthe above process to form the organic anti-reflective coating. Suchorganic anti-reflective coating can absorb distant-ultraviolet (DUV) raytransmitting the photoresist film and reaching to the organicanti-reflective coating, thereby preventing diffused light reflectionfrom the bottom layer of the photoresist film.

In this case, the organic anti-reflective coating becomes insoluble inthe photoresist solution to be applied over the coating because of thecross-linkage bond formed between both of the polymers with the formulaeI and II.

In a further aspect of the present invention, there is provided a methodfor forming pattern on a semiconductor device comprising the steps of:(a) coating the organic anti-reflective coating composition of thepresent invention on the top portion of a film layer to be etched; (b)conducting the baking process for the obtained material to generate thecross-linkage bond and form the resultant organic anti-reflectivecoating; (c) applying a photoresist on the top portion of the organicanti-reflective coating, exposing and developing the photoresist film toproduce the desired photoresist pattern; (d) etching the organicanti-reflective coating by using the obtained photoresist pattern as anetching mask, in turn, the film layer to be etched, thereby forming apattern on the film layer to be etched.

The patterning process of the present invention, the baking process ispreferably performed at 150 to 250° C. for 1 to 5 minutes.

With respect to the patterning process of the present invention, theprocess may further comprise an additional baking process before orafter the exposure process, which is preferably conducted at 70 to 200°C.

Although the anti-reflective coating composition and the patterningprocess according to the present invention are mostly adapted toultrafine pattern formation processes using an ArF light source, theycan be also applied to other ultrafine pattern formation processes usingKrF, DUV including EUV, E-beam, X-ray or ionic beam.

In a still aspect of the present invention, there is provided asemiconductor device produced by the patterning process according to thepresent invention mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the present invention will become apparentfrom the following description of examples with reference to theaccompanying drawing in which:

FIG. 1 is an electron microscopic photograph illustrating a patternformed by a pattern formation process according to one example of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT EXAMPLES

The present invention is now described in a further detail withreference to examples, which are only illustrative and are not intendedto limit the scope of the invention in any way.

Example 1

Synthesis of Light Absorbent Agent Polymer

20 g of maleic anhydride and 19 g of 5,8-dihydroxy-1,4-naphthoquinone(0.5% by mole per maleic anhydride) were dissolved in 26 g of PGMEA. Thedissolved mixture was added with 0.5 g of AIBN to form a vacuumcondition then reacted at 65° C. for 7 hours. After completing thereaction, the solvent was removed from the obtained solution by means ofan evaporator. Thereafter, the treated solution was put under depositionand filtration processes in distilled water, then washed by usingethylether several times to produce the light absorbent agent polymer offormula I (yield 40%).

Molecular weight: 7,000.

Example 2

Preparation of Organic Anti-Reflective Coating Composition

1 g of the light absorbent agent polymer prepared from Example 1 and 0.4g of the cross-linking agent polymer of formula III were dissolved in asolvent mixture comprising 4 g of propylene glycol methylether acetatesolvent; 10 g of methyl 3-methoxy propionate solvent; 10 g of2-heptanone solvent; and 7 g of tetrahydrofurane solvent. After adding0.1 g of the thermal acid generator having the structure represented bythe formula VII to the resultant material to be dissolved, the dissolvedmixture passed through a filter to produce the desired organicanti-reflective coating composition.

Example 3

Formation of Organic Anti-Reflective Coating and Photoresist Pattern

On a silicone wafer, a spin-coating was carried out with the organicanti-reflective coating composition prepared in Example 2, then a bakingprocess was conducted for the obtained material at 215° C. for 2 minutesto generate the cross-linkage bond and form the desirableanti-reflective coating. Thereafter, the obtained anti-reflectivecoating was put under a coating process with a so-called Keum Hopetroleum photosensitive agent (the name of generally used photoresistmaterials) and another baking process at 110° C. for 90 seconds. Afterconducting the above baking process, the baked product was exposed to alight source by means of an ASML/900 scanner apparatus, then, under anadditional baking process at 130° C. for 90 seconds. The exposed waferwas developed using an aqueous solution of 2.38% by weight of TMAH. Fromthe developed material, produced was the pattern shown in FIG. 1.

As above mentioned, the present invention provides a polymer of formulaI useable as a light absorbent agent for organic anti-reflective coatingcomposition, which can form a cross-linkage bond with a cross-linkingpolymer containing acetal groups effective to give solvent-resistance tothe finally formed anti-reflective coating and to prevent under-cuttingand/or putting phenomena. Furthermore, the polymer of formula Icomprises a chromophore having higher absorbance to a 193 nm lightsource, thereby efficiently controlling interference phenomenon of lightat such light source.

Briefly, according to the present invention, it is possible to providean organic anti-reflective composition comprising the polymer mentionedabove and a pattern formation process using the same, whereby animproved perpendicular pattern can be obtained in ultra-fine patternformation processes using a 193 nm light source, and the presentinvention can significantly contribute to the high integration of asemiconductor device.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A light absorbent agent polymer for organic anti-reflectivereflective coating represented by the following formula I:

wherein a and b represent the mole percent of respective monomers anda:b=5 to 95:5 to
 95. 2. A method for preparing a light absorbent agentpolymer for organic anti-reflective coating, comprising the steps of:dissolving maleic anhydride and 5,8-dihydroxy-1,4-naphthoquinone in anorganic solvent; adding a polymerization initiator to the dissolvedmaterial; and producing a polymer represented by the following formula Iby polymerizing the dissolved material under vacuum condition, at 60 to70° C. for 6 to 12 hours:

wherein a and b represent the mole percent of respective monomers anda:b=5 to 95:5 to
 95. 3. The method according to claim 2, wherein theorganic solvent comprises at least one selected from a group consistingof tetrahydrofuran, cyclohexanone, dimethyl formamide, dimethylsulfoxide, dioxane, methylethylketone, PGMEA, ethylacetate, benzene,toluene and xylene.
 4. The method according to claim 2, wherein thepolymerization initiator comprises any one selected from a groupconsisting of 2,2′-azobis isobutyronitrile (AIBN), benzoyl peroxide,acetyl peroxide, lauryl peroxide, t-butyl peracetate, t-butylhydroperoxide and di-t-butyl peroxide.
 5. An organic anti-reflectivecoating composition comprising: a light absorbent agent polymerrepresented by the following formula I; a cross-linking polymerrepresented by the following formula II; a thermal acid generator; andan organic solvent.

wherein a and b represent mole percent of respective monomers and a:b=5to 95% by mole: 5 to 95% by mole.

wherein R₄ and R₅ represent independently alkyl groups having 1 to 10carbon atoms substituted by branched chain or main chain; R₃ is hydrogenor methyl group; and c:d=5 to 90% by mole: 10 to 95% by mole.
 6. Thecomposition according to claim 5, wherein the polymer represented by theformula II comprises at least one selected from a groups consisting ofpolymers having the structures of the following formulae III to VI.

wherein a:b=5 to 90% by mole: 10 to 95% by mole.
 7. The compositionaccording to claim 5, wherein the thermal acid generator comprises thecompound having the structure of the following formula VII.


8. The composition according to claim 5, wherein the organic solventcomprises at least one selected from a group consisting of methyl3-methoxy propionate (MMP), ethyl 3-ethoxy propionate (EEP),propyleneglycol methylether acetate (PGMEA) and cyclohexanone.
 9. Thecomposition according to claim 5, wherein the amount of the lightabsorbent agent is 0.3 to 70% by weight with respect to the organicsolvent contained in the organic anti-reflective coating composition andthe amount of the cross-linking agent in an amount ranging from 0.3 to50% by weight with respect to the organic solvent contained in theorganic anti-reflective coating composition.
 10. The compositionaccording to claim 7, wherein the thermal acid generator is 0.5 to 40%by weight with respect to the total amount of light absorbent agent andcross-linking agent.
 11. A method for forming pattern on a semiconductordevice comprising the steps of: (a) coating the organic anti-reflectivecoating composition according to any one of claims 5 to 7 on the topportion of a film layer to be etched; (b) conducting the baking processfor the obtained material to generate the cross-linkage bond and formthe resultant organic anti-reflective coating; (c) applying aphotoresist on top portion of the organic anti-reflective coating,exposing and developing the photoresist to produce the desiredphotoresist pattern; and (d) etching the organic anti-reflective coatingby using the obtained photoresist pattern as an etching mask, in turn,the film layer to be etched, thereby forming a pattern on the film layerto be etched.
 12. The method according to claim 11, wherein the bakingprocess is carried out at 150 to 250° C. for 1 to 5 minutes.
 13. Themethod according to claim 11, wherein a baking process is additionallycarried out before or after exposure in the photoresist patternformation step.
 14. The method according to claim 13, wherein the bakingprocess is carried out at 70 to 200° C.
 15. A semiconductor deviceproduced by the pattern formation method of claim 11.